Oracle DBMS Interview Question and Answers

17. Give some examples of join methods?
  Some examples of join methods are given as follows:
  • Merge Join - Sorts both the joining tables by using the join key and then merges the sorted rows.
  • Nested loop join - Applies filter conditions specific to the outer table and gets a result set. After that, it joins the inner table with the result set using either an index or a full table scan.
  • Hash join - Uses hash algorithm for filter conditions on smaller table first and then performs the same hashing algorithm on the other table for joined columns. After that, it returns the matching rows.
 
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18. What is database designing?
  Database designing is a process, which follows the requirement analysis phase to determine the required database structure to satisfy application product, or business requirements as per the given criteria.
 
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19. What is join dependency?
  A join dependency is a situation where a table can be created by joining two or more tables.
 
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20. What is the difference between logical data model and physical data model?
  Physical data model depits database in terms of physical objects, such as tables and constrainst; whereas logical data model depicts database in terms of logical objetcs, such as entities and relatioship, and it is represented by the entity relationship model.
 
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